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In this study, the total uranium concentration was determined in groundwater samples used for irrigation and/or drinking purposes and collected from private wells in Al Sharqiya region, Saudi Arabia. The uranium concentrations were measured by laser fluorimetry preceded by radiochemical treatment to eliminate the quenching effect due to the high total dissolved solids content in the groundwater samples. For method validation, some of the measured samples were analyzed for uranium isotopic activities and measured by alpha spectrometry. The results of the uranium concentrations obtained by laser fluorimetry and alpha spectrometry were in good agreement. The uranium concentrations in all the samples were below the World Health Organization (WHO) recommended limit of 30 μg L. Two different approaches were followed to assess the annual effective dose from the ingestion of uranium in the analyzed groundwater samples. The annual effective doses determined by the two approaches were found to be in agreement, and varied from 2.9 to 10.2 μSv y, with a mean value of 6.1 μSv y, which is far below the WHO recommended level of 100 μSv/y. The modified laser fluorimetric procedure was found to be a good tool compared with other techniques for direct measurement of uranium concentrations in high total dissolved solids groundwater samples at low levels.

In this work, experimental isotherms of silver on hexahelicene and heptahelicene were collected at five adsorption temperatures using the quartz crystal microbalance strategy. Two analytical models of statistical physics (MMPG and MMRG) were applied to explain the complexation process of the two helicenes. Based on the physical significance of the two models’ parameters, the silver adsorption was found to be typical to an endothermic phenomenon by the intermediate of the steric variables. Thus, the fitted values of the adsorbed amounts at saturation (QS1 and QS2) were the highest in the case of heptahelicene adsorption. The van der Waals parameters (cohesion pressure a and covolume b) involved in the MMRG model explain the decrease of hexahelicene isotherms at high concentration through the lateral interactions between the adsorbates. Interestingly, the analysis of the complexation energies [|(−E1)| and |(−E2)|] indicated the strongest interaction of silver–[7]helicene. The novel clarifications of the physicochemical description of adsorption isotherms indicated that the heptahelicene can form a stable complex with silver ions.

Twenty-six brands of canned tuna and sardines imported from several countries in Southeast Asia to consume in the KSA. All samples were prepared and analyzed by using a High Pure Germanium Detector of 40% efficiency. Natural radionuclides 40K, 238U (226Ra) and 232Th(228Ra) series were observed with a varying range in all analyzed samples. The values found to be 192.3 ± 14.6, 1.5 ± 0.8 and 1.0 ± 0.6 Bq kg-1 for canned tuna and 219.8 ± 15.8, 0.37 ± 0.3 and 1.2 ± 0.3 Bq kg-1 for canned sardines, respectively. Cesium-137 was not detected at any sample. The comparison between the average activity concentrations of 40K, 238U(226Ra) and 232Th(228Ra) in both canned tuna and sardines was performed and discussed. The dose assessment due to consume/ingestion of seafood was calculated and observed that the calculated committed effective dose is within the global internal dose (290 μSv/y).